$149 for that Mongoose? That's a pretty sweet deal. Were the rims 700 Deep V's or regular 26"? Gives me a real good idea for a single speed diamond frame from Monkey Wards that I have (bought it for $20, couldn't resist).
On the tires, I've bought several like that from Wal Mart and all I did was leave them on a large flat surface for a few days in warm weather (ok, freaking hot Texas summer weather!) and I had no problems whatsoever. But YMMV.